This legislation amends the Federal Water Pollution Control Act to significantly enhance financial assistance for publicly owned treatment works, particularly in underserved areas. It revises the rules governing Water Pollution Control Revolving Loan Funds, increasing the flexibility and amount of additional subsidization states can provide to eligible recipients. The bill allows states to use a greater portion of their capitalization grants for subsidization, establishing a minimum of 20 percent of these grants for such purposes. A key provision dedicates an additional 10 percent of capitalization grants specifically for rural, small, and tribal publicly owned treatment works. These changes are designed to help ratepayers afford essential wastewater and stormwater services by providing more substantial and targeted financial support.